Limited slip differential using face gears and a pinion housing

ABSTRACT

A differential includes a differential case; a side gear comprising a helical face gear; a helical pinion configured for meshing engagement with the side gear; and a pinion housing configured to support the helical pinion. The pinion housing includes a first face; a second face opposing the first face; a first projection located on the first face; and a second projection located on the second face. In some embodiments, the differential further comprises an actuator configured for engagement with the pinion housing and a plurality of friction plates disposed between the actuator and the differential case. The pinion housing also includes an aperture or hole extending radially inwardly from an outer radial surface of the generally annular ring; and a channel extending from the first face to the second face, wherein the channel is substantially radially aligned with the aperture or hole.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application No.61/186,618, filed 12 Jun. 2009, which is hereby incorporated byreference as though fully set forth herein.

TECHNICAL FIELD

The present invention relates to a housing configured to support pinionsin a differential, and includes a differential incorporating a housingthat is configured to support pinions.

BACKGROUND

Helical face gears for use in differentials are known in the art, as setforth for example, in U.S. Pat. Nos. 3,253,483 and 4,791,832. However,the incorporation of helical face gears into differentials has not beencommonly utilized because of, for example, challenges with respect tothe strength of the gears, which may adversely affect performance of thegear set in the differential and/or limit the torque application.

SUMMARY

A differential comprises a differential case; a side gear comprising ahelical face gear; a helical pinion configured for operative or meshingengagement with the side gear; and a pinion housing. The pinion housingis configured to support the helical pinion and includes: a first face;a second face opposing the first face; a first projection located on thefirst face; and a second projection located on the second face. Inaccordance with some embodiments, the differential further comprises anactuator configured for engagement with the pinion housing. The actuatorcomprises a first face that includes a depression substantiallycorresponding in shape to the first projection or the second projectionon the pinion housing. In accordance with some embodiments, thedifferential further comprises a plurality of friction plates disposedbetween the actuator and the differential case.

A housing is configured to support at least one helical pinion in adifferential and comprises a generally annular ring. The generallyannular ring has a first face and a first projection located on thefirst face and extending in the axial direction of the generally annularring. The generally annular ring also has a second face and a secondprojection located on the second face and extending in the axialdirection of the generally annular ring. The generally annular ring alsohas an aperture or hole extending radially inwardly from an outer radialsurface of the generally annular ring. The generally annular ring alsohas a channel extending from the first face to the second face, whereinthe channel is substantially radially aligned with the aperture or thehole.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawings, wherein:

FIG. 1 is an exploded perspective view of a differential in accordancewith an embodiment of the invention.

FIG. 2 is a cross-sectional view of a differential in accordance with anembodiment of the invention.

FIG. 3 is a perspective view of a pinion housing of the differential ofFIG. 1.

FIG. 4 is a perspective view of a pinion and a side gear of thedifferential of FIG. 1.

FIG. 5 is a perspective view of an actuator of the differential of FIG.1.

FIG. 6 is a perspective view of the actuator of FIG. 5 disposed in adifferential case of the differential of FIG. 1.

FIGS. 7A-7B are schematic views of force acting on the pinion housing ofFIG. 2.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are described herein and illustrated in theaccompanying drawings. While the invention will be described inconjunction with embodiments, it will be understood that they are notintended to limit the invention to these embodiments. On the contrary,the invention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as embodied by the appended claims.

FIGS. 1-2 generally illustrate an embodiment of differential 10 shown inaccordance with teachings of the present invention. Differential 10 maycomprise a pinion housing 12. Referring now to FIGS. 1 and 3, pinionhousing 12 may be made from one piece of material (e.g., comprise aunitary, integral, and/or monolithic structure) in accordance with anembodiment of the invention. Pinion housing 12 may be generallyring-shaped in accordance with an embodiment of the invention. Pinionhousing 12 may comprise an outer radial surface 14 that extendscircumferentially around the pinion housing 12. Pinion housing 12 mayfurther comprise a first face 16 and a second face 18. The second face18 may oppose the first face 16.

The pinion housing 12 may include a first projection 20 located on thefirst face 16. The first projection 20 may extend in the axial directionof the generally annular ring comprising the pinion housing 12. Thepinion housing 12 may further include a second projection 22 located onthe second face 18. The second projection 22 may extend in the axialdirection of the generally annular ring comprising the pinion housing12. The pinion housing 12 may include a single projection 20 on thefirst face 16, and a single projection 22 on the second face 18 in anembodiment of the invention. The pinion housing 12 may include aplurality of projections 20 on the first face 16 and/or a plurality ofprojections 22 on the second face 18 in accordance with some embodimentsof the invention. At least one of the first projections 20 may comprisea ramp or a wedge in accordance with an embodiment of the invention.Each of the first projections 20 may comprise a ramp or a wedge inaccordance with an embodiment of the invention. At least one of thesecond projections 22 may comprise a ramp or a wedge in accordance withan embodiment of the invention. Each of the second projections 22 maycomprise a ramp or a wedge in accordance with an embodiment of theinvention.

At least one of the first projections 20 may comprise a plurality ofsurfaces in accordance with an embodiment of the invention. For exampleand without limitation, at least one of the surfaces may besubstantially parallel to the first face 16, and at least one of thesurfaces may be substantially angled relative to the first face 16. Atleast one of the second projections 22 may comprise a plurality ofsurfaces in accordance with an embodiment of the invention. For exampleand without limitation, at least one of the surfaces may besubstantially parallel to the second face 18, and at least one of thesurfaces may be substantially angled relative to the second face 18. Inaccordance with an embodiment of the invention, at least one of thefirst projections 20 and/or second projections 22 may comprise aboutthree surfaces. Although a ramp or wedge comprising three surfaces ismentioned in detail and generally illustrated, the first and secondprojections 20, 22 may comprise fewer or more surfaces in accordancewith various embodiments of the invention.

Pinion housing 12 may be configured for locating and/or supporting oneor more pinions 24. The pinions 24 may be disposed in a radial patternor the pinions 24 may be circumferentially spaced around thecircumference of the pinion housing 12. The pinion housing 12 may have aplurality of radially inwardly extending apertures or holes 26. Theapertures 26 may extend radially inwardly into the pinion housing 12from the outer radial surface 14 of the pinion housing 12. The apertures26 may each have an axis that extends substantially radially outwardlyfrom the approximate center of the pinion housing 12. At least one ofthe first projections 20 of the pinion housing 12 may be locatedproximate aperture 26. At least one of the second projections 22 of thepinion housing 12 may be located proximate aperture 26. For exampleonly, and without limitation, there may be approximately six apertures26 extending through the pinion housing 12. Although six apertures 26are mentioned in detail, there may be fewer or more apertures 26 inother embodiments of the invention. The apertures 26 may beequi-angularly spaced around the circumference of the pinion housing 12.Although the apertures 26 are described as being equi-angularly spacedaround the circumference of the pinion housing 12, the apertures 26 maybe spaced in any alternate arrangements and/or configurations in otherembodiments of the invention.

The pinion housing 12 may further comprise an inner radial surface 28.The pinion housing 12, including the inner radial surface 28 may beconfigured to restrain the pinions 24 from axial movement. The innerradial surface 28 may extend circumferentially around the pinion housing12, such that each of apertures 26 may comprise a blind aperture. Forexample, a first end of the aperture 26 at the outer radial surface 14may be open, while a second end of the aperture 26 at the inner radialsurface 28 may be closed. The second end of the aperture 26 may opposethe first end of the aperture 26. The pinion housing 12 may furtherinclude a channel 30 extending from the first face 16 to the second face18 of the generally annular ring of the pinion housing 12. The channel30 may be substantially aligned with the apertures 26 (e.g.,substantially radially aligned with the apertures 26). Further, thenumber of channels 30 may generally correspond to the number ofapertures 26 in the pinion housing 12, although fewer or more channels30 than the number of apertures 26 may be used in embodiments of theinvention. The pinion housing 12 may be configured to support thepinions 24 to be in operative or meshing engagement with side gears 32.The pinion housing 12 has been removed in FIG. 4 for illustrativepurposes, and FIG. 4 generally illustrates the operative or meshingengagement between pinions 24 and side gears 32. As generally describedand illustrated, the pinion housing 24 may exert pressure on the pinions24 to move them around and/or about an axial center line of the sidegears 32.

Still referring to FIGS. 1-3, the differential 10 may comprise thepinions 24. Pinion 24 may comprise a helical pinion. Accordingly, pinion24 may include a number of helical teeth. The number of helical teethand the geometry of the tooth flank of the helical teeth may vary inaccordance with various embodiments of the invention. The helical pinion24 may be generally cylindrical in accordance with an embodiment of theinvention, although the shape of the helical pinion may vary inaccordance with various embodiments of the invention. There may be aplurality of pinions 24 in some embodiments of the invention. The numberof the pinions 24 in the differential 10 may vary. However, there maygenerally be at least two pinions 24. The number of pinions 24 may beabout six in an embodiment, although greater or fewer pinions 24 may beused in other embodiments. The number of pinions 24 may generallycorrespond to the number of apertures 26 in the pinion housing 12,although fewer pinions 24 in relation to the number of apertures 26 maybe used in embodiments of the invention. In these embodiments of theinvention, at least one or more of the apertures 26 may remain open. Thesize of pinions 24 may also vary, but may generally be sized so as tofit operatively within the apertures 26 of the torque ring so as toallow the pinions 24 to be free to rotate within apertures 26. Thepinions 24 may generally be axially trapped between the inner radialsurface 28 of the pinion housing 12 and an inner surface of adifferential case (or other housing for the pinion housing 12).

Referring now to FIGS. 1-2 and 4, the differential 10 may furthercomprise the side gears 32. Side gears 32 may have a helical face (i.e.,comprise helical face gears). Accordingly, side gears 32 may include anumber of helical teeth. The number of helical teeth and the geometry ofthe tooth flank of the helical teeth may vary in accordance with variousembodiments of the invention. The use of forging technology in place ofmachine-cutting technology for the side gears 32 may significantlyimprove the strength of side gears 32. Accordingly, helical face gearscomprising the side gears 32 may be robust and well-supported. The useof high strength helical face gears may allow for higher torqueapplication and provide a wider range of torque bias ratio. In addition,the compact size of side gears 32 comprising helical face gears inconnection with a pinion housing 12 may allow for greater flexibility inpackaging and design, thereby increasing the transportability of adifferential that includes the side gears 32. In particular, helicalface technology may allow for the use of the side gears 32 in connectionwith various packaging designs of various models of motor vehicles. Thecompact size of side gears 32 comprising helical face gears inconnection with a pinion housing 12 may also allow for the direction ofdynamic forces in a more beneficial way.

The helical face of each side gear 32 may face pinion housing 12. Theside gears 32 may be configured to be in operative or meshing engagementwith the pinions 24. In particular, the helical teeth of the side gears32 may be in an operative, or meshing, engagement with the helical teethof the pinions 24. Both the helical teeth of the side gears 32 and thehelical teeth of the pinions 24 may extend into channels 30 in thepinion housing 12. With a configured meshing engagement between thepinions 24 and the side gears 32, the side gears 32 may be forced toturn about their axis. The side gears 32 may be configured to transmittorque from the pinions 24 to an output (e.g., axle shafts of a motorvehicle). Because the output (e.g., axles shafts) are grounded andcoupled to the side gears 32, a motor vehicle incorporating thedifferential 10 may move. When the side gears 32 rotate at differentspeeds by grounding through the output (e.g., axle shafts), the pinions24 may rotate within the pinion housing 12 and in mesh with the sidegears 32 to compensate. A first and second side gear 32 may be disposedon opposing sides of the pinion housing 12. Each side gear 32 may have afirst annular hub portion 34 that is configured to receive an axle shaft(not shown) of a motor vehicle, for example. An inner radial surface ofthe first annular hub portion 34 of the side gear 32 that may include aplurality of splines. The axle shafts may connect to side gears 32through a splined interconnection with the splines.

Referring now to FIGS. 1-2 and 5, the differential 10 may furthercomprise an actuator 36. Actuator 36 may be configured for engagementwith the pinion housing 12. Actuator 36 may be generally ring-shaped inaccordance with an embodiment of the invention. Actuator 36 may comprisean outer radial surface 38 that extends circumferentially around theactuator 36. Actuator 36 may further comprise a first face 40 and asecond face 42. The second face 42 may oppose the first face 40. Theactuator 36 may include a depression 44 located on the first face 40.The actuator 36 may include a single depression 44 on the first face 40in an embodiment of the invention. The actuator 36 may include aplurality of depressions 44 on the first face 40 in accordance with someembodiments of the invention. The depression 44 may generally correspondin shape to the first projection 20 or the second projection 22 on thepinion housing 12. The first face 40 may be configured to face thepinion housing 12 in an embodiment of the invention.

At least one of the depressions 44 may comprise a plurality of surfacesin accordance with an embodiment of the invention. For example andwithout limitation, at least one of the surfaces may be substantiallyparallel to the first face 40, and at least one of the surfaces may besubstantially angled relative to the first face 40. In accordance withan embodiment of the invention, at least one of the depressions 44 maycomprise about three surfaces. Although a depression comprising threesurfaces is mentioned in detail and generally illustrated, thedepression 44 may comprise fewer or more surfaces in accordance withvarious embodiments of the invention. The second face 42 of the actuator36 may be generally or substantially flat in accordance with anembodiment of the invention. For example and without limitation, thesecond face 42 of the actuator 36 may not have a depression. The outerradial surface 38 of the actuator 36 may comprise at least one and/or aplurality of radially extending tabs 46. For example and withoutlimitation, the actuator 36 may include three tabs 46. Although threetabs 46 are mentioned in detail and generally illustrated, the actuatormay have fewer or more tabs 46 in accordance with other embodiments ofthe invention. The tabs 46 may be equi-angularly spaced around thecircumference and/or periphery of the actuator 36. Accordingly, the tabs46 may be approximately 120° apart in accordance with an embodiment ofthe invention. Tabs 46 may be generally configured for engagement withthe differential case 50. For example and without limitation, tabs 46may be configured for engagement with slots in the differential case 50.FIG. 6 generally shows the actuator 36 disposed in differential case 50.In accordance with an embodiment of the invention, torque may betransferred from the differential case 50 to the actuator 36. Theactuator 36 may be configured to drive the pinion housing 12. Theactuator 36 may be configured to lock the pinions 24 with both sidegears 32, pushing both friction plate assemblies 48 and transferringtorque to both wheels of a motor vehicle (not shown) simultaneously.

Referring to FIGS. 1-2, the differential 10 may further comprisefriction plate assemblies 48 (e.g., a plurality of friction plates). Thefriction plate assemblies 48 may be disposed on both sides of the pinionhousing 12. The friction plate assemblies 48 may be disposed between theactuator 36 and the differential case 50. At least one of the pluralityof friction plates of the friction plate assembly 48 may include acoating. For example, at least one of the plurality of friction platesof the friction plate assembly 48 may include a coating configured toaid the friction plates to react to movement between the side gears 32and the differential case 50. The axial force exerted by the actuator 36may generally depend on the input torque and the ramp or wedge angle onthe actuator 36. During turning of the motor vehicle at higher speeds onhigh coefficient surfaces, both of the wheels may have differentresistive torque and rotational speed. As the torque capacity of thefriction plate assemblies 48 is less than the torque available at boththe side gears 32, differential action may make the friction plateassemblies 48 slip and allow the outer wheel to rotate faster than theinner wheel, for example. If one wheel slips as a result of a lowfriction surface beneath the wheel, the pinion housing 12 may beconfigured to generate an axial force against the actuator 36. Referringnow to FIGS. 7A-7B, a schematic of the reaction force is generallyillustrated. This may result in compression of the friction plateassemblies 48 against the side gears 32, thereby transferring torquefrom the differential case 50 to the side gear 32 through the frictionplate assembly 48. In FIG. 7B, the axial force F_(a) generated againstthe actuator 36 by the ramp or wedge 22 on pinion housing 12 maygenerally be in accordance with the following equation: F_(a)=F/tan φ,where F is the input force and φ is the ramp or wedge angle on the rampor wedge 22 of the pinion housing 12.

Differential case 50, along with cover 52, may be provided to house thepinion housing 12, the pinions 24, the side gears 32 and/or any numberof other components of the differential 10. The differential 10 mayfurther include a ring gear (not shown). The ring gear may be connectedto an input source and/or drive source (not shown) in a conventionalmanner for rotating the differential case 50. The differential 10 mayfurther include thrust washers 54. Thrust washers 54 may be providedbetween a thrust face of the differential case 50 and a thrust face ofthe side gear 32 and between a thrust face of the cover 52 and a thrustface of the side gear 32. Thrust washers 54 may be provided to controlbacklash, as the friction pack assemblies 48 may become isolated fromthe axial thrust force of the side gears 32.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and various modifications andvariations are possible in light of the above teaching. The embodimentswere chosen and described in order to explain the principles of theinvention and its practical application, to thereby enable othersskilled in the art to utilize the invention and various embodiments withvarious modifications as are suited to the particular use contemplated.The invention has been described in great detail in the foregoingspecification, and it is believed that various alterations andmodifications of the invention will become apparent to those skilled inthe art from a reading and understanding of the specification. It isintended that all such alterations and modifications are included in theinvention, insofar as they come within the scope of the appended claims.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

1. A differential, comprising: a differential case; a side gear comprising a helical face gear; a helical pinion configured for meshing engagement with the side gear; and a pinion housing configured to support the helical pinion, wherein the pinion housing includes: a first face; a second face opposing the first face; a first projection located on the first face; and a second projection located on the second face.
 2. The differential of claim 1, wherein the first and second projections extend in the axial direction of the pinion housing.
 3. The differential of claim 1, wherein the first projection comprises a ramp.
 4. The differential of claim 1, wherein the second projection comprises a ramp.
 5. The differential of claim 1, wherein the first projection comprises a plurality of surfaces.
 6. The differential of claim 1, wherein the second projection comprises a plurality of surfaces.
 7. The differential of claim 5, wherein at least one of the plurality of surfaces is substantially parallel to the first face.
 8. The differential of claim 7, wherein at least one of the plurality of surfaces is substantially angled relative to the first face.
 9. The differential of claim 1, wherein the pinion housing comprises an aperture or hole extending radially inwardly from an outer radial surface of the torque ring.
 10. The differential of claim 9, wherein the first projection is located proximate the aperture.
 11. The differential of claim 1, further comprising an actuator configured for engagement with the pinion housing.
 12. The differential claim of 11, wherein the actuator comprises a first face that is configured to face the pinion housing and the first face of the actuator includes a depression.
 13. The differential of claim 12, wherein the depression substantially corresponds in shape to the first projection.
 14. The differential of claim 12, wherein the depression comprises a plurality of surfaces, wherein at least one of the plurality of surfaces is substantially parallel to the first face, and wherein at least one of the plurality of surfaces is substantially angled relative to the first face.
 15. The differential of claim 11, wherein the actuator comprises a radially extending tab configured for engagement with the differential case.
 16. The differential of claim 11, further comprising a plurality of friction plates disposed between the actuator and the differential case.
 17. The differential of claim 16, wherein at least one of the plurality of friction plates includes a coating.
 18. A housing configured to support at least one helical pinion in a differential, the housing comprising: a generally annular ring having: a first face; a first projection located on the first face and extending in the axial direction of the generally annular ring; a second face opposing the first face; a second projection located on the second face and extending in the axial direction of the generally annular ring; an aperture or a hole extending radially inwardly from an outer radial surface of the generally annular ring; a channel extending from the first face to the second face of the generally annular ring, wherein the channel is substantially radially aligned with the aperture or the hole.
 19. The housing of claim 18, wherein the first projection and the second projection each comprise a ramp.
 20. A differential, comprising: a differential case; a side gear comprising a helical face gear; a helical pinion configured for meshing engagement with the side gear; a pinion housing configured to support the helical pinion, wherein the pinion housing includes: a first face; a second face opposing the first face; a first projection located on the first face; a second projection located on the second face; an actuator configured for engagement with the pinion housing, wherein the actuator comprises a first face that includes a depression corresponding in shape to the first projection or the second projection; and a plurality of friction plates disposed between the actuator and the differential case. 